public class MyLinkedList {
    static class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;
        public ListNode(int val){
            this.val=val;
        }
    }

    public ListNode head;
    public ListNode last;

    //头插法
    public void addFirst(int data){
        ListNode listNode=new ListNode(data);
        if(head==null){
            head=listNode;
            last=listNode;
        }else{
            listNode.next=head;
            head.prev=listNode;
            head=listNode;
        }
    }

    //尾插法
    public void addLast(int data){
        ListNode listNode=new ListNode(data);
        if(head==null){
            head=listNode;
            last=listNode;
        }else{
            last.next=listNode;
            listNode.prev=last;
            last=listNode;
        }
    }

    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index<0||index>size()){
            System.out.println("插入位置错误！！！");
            return;
        }
        if(index==0){
            addFirst(data);
            return;
        }
        if(index==size()){
            addLast(data);
            return;
        }
        ListNode cur=findIndex(index);
        ListNode listNode=new ListNode(data);
        listNode.next=cur;
        cur.prev.next=listNode;
        listNode.prev=cur.prev;
        cur.prev=listNode;
    }
    private ListNode findIndex(int index){
        ListNode cur=head;
        while (index!=0){
            cur=cur.next;
            index--;
        }
        return cur;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur=head;
        while (cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode cur=head;
        while (cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head!=null){
                        head.prev=null;
                    }
                }else{
                    cur.prev.next=cur.next;
                    if(cur.next!=null){
                        cur.next.prev=cur.prev;
                    }else{
                        last=last.prev;
                    }
                }
                return;
            }
            cur=cur.next;
        }
    }

    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur=head;
        while (cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head!=null){
                        head.prev=null;
                    }
                }else{
                    cur.prev.next=cur.next;
                    if(cur.next!=null){
                        cur.next.prev=cur.prev;
                    }else{
                        last=last.prev;
                    }
                }
            }
            cur=cur.next;
        }
    }

    //得到单链表的长度
    public int size(){
        int len=0;
        ListNode cur=head;
        while (cur!=null){
            len++;
            cur=cur.next;
        }
        return len;
    }

    public void display(){
        ListNode cur=head;
        while (cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
        System.out.println();
    }

    public void clear(){
        ListNode cur=head;
        while (cur!=null){
            ListNode curNext=cur.next;
            cur.prev=null;
            cur.next=null;
            cur=curNext;
        }
        head=null;
        last=null;
    }

}





